A thermal interface transfers heat between two objects, such as a heat source and a heat sink. A thermal interface is often used to remove heat generated from an electronic device. A small temperature difference between a hot side and a cold side of the thermal interface (e.g., when the thermal interface is exposed to external or environmental loads, such as higher temperatures/solar radiation) causes the thermal interface to become less effective at rejecting heat from the electronic device. In some operating conditions, the thermal interface is unable to remove a sufficient amount of heat from the electronic device or actually transfers heat from the external source or environment to the electronic device, thus damaging the electronic device.
In the context of a spacecraft (e.g., a spaceship, a satellite, or a space station), as the spacecraft operates (e.g., orbits an astronomical body) the spacecraft typically has one surface that experiences relatively high environmental loading and has another surface that experiences relatively low environmental loading. For example, the surface of the spacecraft that faces the Sun experiences high solar radiation and temperatures as compared to the surface of the spacecraft facing away from the Sun. The surface that faces the Sun may change over time as the spacecraft operates. In some operating conditions, the surface that faces the Sun cannot be used effectively to transfer or reject heat into space from the spacecraft and/or electronic devices thereof.
Additionally, generally only surfaces that are protected from high levels of solar radiation can be used as radiative surfaces. This limitation on which surfaces can be used means that some surfaces (e.g., surfaces that face the Sun) cannot be used to reject heat. Alternatively, complicated protection schemes, such as a thermal shield (e.g., louvers or blinds) may be used to reflect solar radiation from the Sun and reduce the amount of solar radiation absorbed by the radiative surfaces and the thermal interface. Variable conductance heat pipes may be used throughout the spacecraft to transfer heat from electronic devices to a radiative surface that transfers (e.g., rejects) heat into space. Alternatively, a spacecraft may include heat pumps to transfer (or pump) the heat from the electronic device to the radiative surface. These solutions to reject heat energy add complexity, weight, and volume to spacecraft design. In the context of a spacecraft, these factors greatly increase cost.